1. Field of the Invention
2. Technical Field
This invention relates to a retractable type writing instrument wherein an operating member movable relative to an exterior body through operation is interlocked with a refill body having a nib at its tip, an engagement portion for engaging an engagement protrusion formed on an inner surface of a clip attached to the exterior body is formed on the operating member, the engagement protrusion is engaged with the engagement portion, thereby locking the nib of the refill body in a state of the nib projected from a tip of the exterior body, and the locking of the nib in its projected position is released by an operation to be made in the same direction as the operation for locking the nib in its projected position.
As one example, there is Japanese Patent Unexamined Publication (Kokai) No. H09-99691. A retractable type writing instrument disclosed in this publication is constructed such that a unidirectionally rotating cam mechanism consisting of a plurality of members is disposed in a barrel and projection and retraction of a refill received in the barrel is locked/released by repeating a pressing operation with respect to a knock part.
In a conventional retractable type writing instrument having a sliding member as in a knock type ballpoint pen, a material having a high wear resisting property, a low friction coefficient and a good slidability is used as the material of the sliding member. Moreover, a biasing force of a coiled spring for biasing a refill as an ink reservoir member backward is set to a low load value so that the projecting and retracting operation of the nib can be performed with a least possible force.
In the conventional techniques as mentioned above, however, the following problems are involved. Although they have such a mechanism in which a locking/releasing operation for a projection/retraction of a writing body is performed by a pressing operation of a pressing body, a mechanism for locking/releasing the projection and retraction is complicated, the number of component parts is increased, an assembling operation is cumbersome and the cost is increased. In addition, since the conventional techniques are constituted by incorporating the mechanism in a rear part of an interior of the barrel, there is encountered with such a problem that the length of the barrel must be increased.
As for operability of the retractable type writing instrument, the matter is not so simple as that reduction of a friction coefficient of the operating member will naturally provide enhancement of operability of the writing instrument. Instead, sureness and reliability of the locking of the projection/retraction through operation and actual feel of the operation are required. For example, in the case where the friction coefficient is too low, the operating member tends to move overly and slide, which may possibly result in an unlocked state. In contrast, if the operation is made with such a slight force as giving the operator (i.e., user) a feel of almost no load, the operator can hardly receive an actual feel that he/she has projected/retracted the nib and therefore, he/she must take the trouble to visually ascertain the locking state of the nib each time.
Furthermore, in the writing instrument wherein the biasing force of the coiled spring for biasing the refill backward is set to a low load value as mentioned above, when, for example, the writing instrument should be directly put into a pocket after use, the knock member would be most likely accidentally pressed, thus allowing the nib to be projected. This would, in many cases, result in a disaster that the operator""s clothes get stained.
It is an object of the present invention to provide, in view of the shortcomings and problems inherent in the above-mentioned conventional techniques, an improved retractable type writing instrument.
A first subject matter of the present invention resides in a retractable type writing instrument wherein an operating member movable relative to an exterior body through operation is interlocked with a refill body having a nib at its tip, an engagement portion for engaging an engagement protrusion formed on an inner surface of a clip attached to the exterior body is formed on the operating member, the engagement protrusion is engaged with the engagement portion, thereby locking the nib of the refill body in a state of the nib projected from a tip of the exterior body, and the locking of the nib in its projected position is released by an operation to be made in the same direction as the operation for locking the nib in its projected position, the retractable writing instrument being characterized in that when the engagement protrusion and the engagement portion are to be engaged with or disengaged from each other by the operation, a relative movement between the engagement protrusion and the engagement portion at the time of engagement or disengagement consists of a combination of a movement in a same plane direction and a movement towards or away from the plane.
A second subject matter of the present invention resides in a retractable type writing instrument wherein a clip including an attachment basal portion with respect to an exterior body having a nib projection hole at a tip thereof, a deformation plate portion as an intermediate part and an engagement protrusion at an inner surface of the deformation plate portion is arranged outside the exterior body, a refill body having a nib at a tip thereof and storing therein ink is received in the exterior body such that the refill body can move back and forth in a state in which the refill body is biased backward by a coiled spring, an operating member is moved to cause the refill body or a connecting member with respect to the refill body to move so that the nib projects from the nib projection hole, the refill body or the member to be connected to the refill body is brought into engagement with the engagement protrusion of the clip, thereby maintaining the projected state of the nib from the exterior body, the operating member is moved again to release the engagement so that the nib is received in the exterior body by a backward biasing force of the coiled spring, the retractable type writing instrument being characterized in that the engagement protrusion of the clip is formed of polycarbonate resin, an engagement portion of the refill body or the member to be connected to the refill body with respect to the engagement protrusion is formed of polyoxymethylene resin, and a surface of the engagement portion and a protruded portion of the engagement protrusion are contacted with each other at the time of an overriding engagement for projecting the nib.
In the present invention, the mechanism for locking/releasing the projection/retraction is simple, the number of component parts is reduced, the assembling operation is easy and the cost is low. In addition, it has such an advantage that since the mechanism for locking/releasing the projection/retraction is not incorporated in a rear part of a barrel, the barrel must be reduced in length to that extent. Moreover, sureness of the locking of the projection/retraction through operation and actual feel of the operation can be obtained. Furthermore, there is no such a fear that the knock member is accidentally pressed after the writing instrument is used and the user""s clothes get stained.